Additional Information
It should be noted that Block Diagram Constants cannot be Strict Type Definitions. When a Constant is tied to a Strict Type Definition, it is simply down-casted to a regular Type Definition.
In contrast, Enums, which are similar in function to Combo Boxes and Rings, do have their own (Enum) data type on the Block Diagram. Again, you can verify this by looking at the data type of its associated wire on the Block Diagram. For this reason, Enum items do update with their Type Definitions.
In order to have Constants update along with their Type Definitions, Enums will need to be used instead of Combo Boxes/Rings. They have their own data type, which makes them much more versatile in how you can read their values on the Block Diagram. To access the selected item's label on the Block Diagram (like a Combo Box would return), simply wire the Enum terminal to the input of the Format Into String function, and the item name will be automatically returned.